Open AccessFracture-induced softening for large-scale ice dynamics
Author(s) -
Torsten Albrecht,
Anders Levermann
Publication year - 2014
Publication title -
the cryosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.574
H-Index - 82
eISSN - 1994-0424
pISSN - 1994-0416
DOI - 10.5194/tc-8-587-2014
Subject(s) - geology , fracture (geology) , mechanics , advection , sea ice growth processes , ice stream , ice sheet , flow (mathematics) , sea ice , softening , pressure ridge , geotechnical engineering , geomorphology , materials science , climatology , arctic ice pack , physics , drift ice , cryosphere , composite material , thermodynamics
Floating ice shelves can exert a retentive and hence stabilizing force ontothe inland ice sheet of Antarctica. However, this effect has been observed todiminish by the dynamic effects of fracture processes within the protectiveice shelves, leading to accelerated ice flow and hence to a sea-levelcontribution. In order to account for the macroscopic effect of fractureprocesses on large-scale viscous ice dynamics (i.e., ice-shelf scale) we applya continuum representation of fractures and related fracture growth into theprognostic Parallel Ice Sheet Model (PISM) and compare the results toobservations. To this end we introduce a higher order accuracy advectionscheme for the transport of the two-dimensional fracture density across theregular computational grid. Dynamic coupling of fractures and ice flow isattained by a reduction of effective ice viscosity proportional to theinferred fracture density. This formulation implies the possibility ofnon-linear threshold behavior due to self-amplified fracturing in shearregions triggered by small variations in the fracture-initiation threshold. Asa result of prognostic flow simulations, sharp across-flow velocity gradientsappear in fracture-weakened regions. These modeled gradients compare well inmagnitude and location with those in observed flow patterns. This modelframework is in principle expandable to grounded ice streams and providessimple means of investigating climate-induced effects on fracturing (e.g.,hydro fracturing) and hence on the ice flow. It further constitutes aphysically sound basis for an enhanced fracture-based calvingparameterization